SEM micrographs of the coated silicon chips dipped in pH solutions. Coated silicon chips were dipped in solutions with pH 2, 4, 7 and 10 to characterize stability of the nanolayers. (a) shows the coated chip after a 15 hours dip in pH 2 solution. (b), (c) and (d) show the surface of the chips after 15 hours dip in solutions at pH 4, 7 and 10, respectively. All scale bars are 20 μm.